1. Field of the Invention
This invention relates to a solvent for loosening and removal of protective surfaces on metals, glasses, plastic, etc., and further relates to a process and composition for removal of protective paper and organic films from the surface of polished metal objects.
2. Description of the Prior Art
Polished metal surfaces such as stainless steel, aluminum, etc. are generally protected during shipment and handling by the application of paper and polymer sheets with an adhesive so that the highly polished metal sheets are protected from scratches, gouges, abrasion and other damage during shipment and during fabrication of the metal into their end usage devices, such as tanks or other similar equipment. Large stainless steel plates used in the fabrication of water storage tanks for the nuclear industry have one surface which is highly polished, usually at the mill. The surface must be properly protected to avoid mechanical and environmental damage in transit to the fabricator or installation site. A paper tape is routinely applied by the polishing vendor and frequently, after transit, may arrive at the work site wet and also may have been exposed to substantial amounts of sunlight and other agents which cause the adhesive-backed paper to become more adherent, tacky or otherwise difficult to remove mechanically. Normal removal by peeling the paper is frequently not possible. The stainless steel plates often remain on the job site for several months, or sometimes years, before and after fabrication into tanks or the like, during which time additional exposure to the elements occurs. This usually results in rendering the paper or other film protective surface most difficult to remove. Various individual solvents have been used in the prior art to attempt to soften and remove the paper or plastic coating, but proved to be ineffective. The solvents would evaporate before they could successfully act upon the adhesive. In addition, many of the solvents utilized contain halogens including fluorine, chlorine and iodine which may result in intergranular corrosion of the stainless steel, or the solvents may contain sulfates which with water form sulfuric or sulfurous acid and can cause chemical attack upon the stainless steel. Such chemical attack on the stainless steel surfaces cannot be tolerated in the tanks being constructed for the nuclear industry. In addition, the method of applying the solvents in the prior art permit selective evaporation of components of the solvent mixture so that within a few minutes the solvent may separate into two phases and be rendered ineffective. Frequently it has been found that mechanical means such as peeling by hand, etc., when applied to freshly applied manufactured paper covered plates of stainless steel, are quite workable; but, extended exposure of the plates with their coating to sunlight and other environmental agents cause the adhesive to be relatively inert or fixed so that they resist removal by normal means.